This function runs a function_exists() check and if the
Suhosin extension <http://www.hardened-php.net/suhosin/> is loaded,
checks if it doesn’t disable the function being checked.

It is useful if you want to check for the availability of functions
such as eval() and exec(), which are dangerous and might be
disabled on servers with highly restrictive security policies.

Note

This function was introduced because Suhosin terminated
script execution, but this turned out to be a bug. A fix
has been available for some time (version 0.9.34), but is
unfortunately not released yet.